Some things we're just born with--hair color, eye color, height. I have also come to believe that our default outlook--positive or negative, optimistic or pessimistic, has to be one of them. Can it be mitigated and controlled? Possibly, for short periods of time. But I don't believe the default setting can be changed.
Or perhaps I say this because, try as I might, I'll never be an optimist. Although, I'm not quite a pessimist, either. I don't think it's a black & white thing, but that I fall into the "perpetually wary" category. I have a hard time with those things I cannot see, and I have a hard time believing in universal benevolence, at least, as far as I, individually, am concerned.
I also believe that some people are lucky, and that luck favors those who know who they are and what they want--consciously or unconsciously. I've never been one of those, either, and it's a trait I've always, always envied. Especially in hindsight. I think I've made unfortunate choices in my life and that, had I known myself better, believed in myself more, I wouldn't have been swayed, and I would have had some insight into my own intuition.
But then we do the best we can with what we have, don't we? I hope so. I take comfort in that, if it's the case. Of course, then that perpetual wariness prods me, whispers dark doubts that I'm too ready to believe.